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Don't allocate when drawing by reusing glyp rend buffer

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This commit is contained in:
bloeys
2022-07-04 01:10:37 +04:00
parent edd8d5b71b
commit 3d7d09744d
4 changed files with 76 additions and 22 deletions
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55
glyphs/glyphs.go
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@ -13,6 +13,9 @@ import (
"github.com/golang/freetype/truetype"
)
const floatsPerGlyph = 11
const maxGlyphsPerBatch = 16384
type GlyphRend struct {
Atlas *FontAtlas
AtlasTex *assets.Texture
@ -22,7 +25,13 @@ type GlyphRend struct {
GlyphMat *materials.Material
GlyphCount int32
GlyphVBO []float32
//NOTE: Because of the sad realities (bugs?) of CGO, passing an array in a struct
//to C explodes (Go pointer to Go pointer error) even though passing the same array
//allocated inside the function is fine (Go potentially can't detect what's happening properly).
//
//Luckily slices still work, so for now we will use our slice as an array (no appending)
GlyphVBO []float32
// GlyphVBO [floatsPerGlyph * maxGlyphsPerBatch]float32
ScreenWidth int32
ScreenHeight int32
@ -43,13 +52,11 @@ func (gr *GlyphRend) DrawTextOpenGLAbs(text string, screenPos *gglm.Vec3, color
//Prepass to pre-allocate the buffer
rs := []rune(text)
const floatsPerGlyph = 18
// startPos := screenPos.Clone()
pos := screenPos.Clone()
advanceF32 := float32(gr.Atlas.Advance)
lineHeightF32 := float32(gr.Atlas.LineHeight)
instancedData := make([]float32, 0, len(rs)*floatsPerGlyph) //This a larger approximation than needed because we don't count spaces etc
for i := 0; i < len(rs); i++ {
r := rs[i]
@ -62,7 +69,6 @@ func (gr *GlyphRend) DrawTextOpenGLAbs(text string, screenPos *gglm.Vec3, color
pos.SetX(pos.X() + advanceF32)
continue
}
gr.GlyphCount++
scale := gglm.NewVec2(advanceF32, lineHeightF32)
@ -73,17 +79,36 @@ func (gr *GlyphRend) DrawTextOpenGLAbs(text string, screenPos *gglm.Vec3, color
drawPos.SetX(drawPos.X())
drawPos.SetY(drawPos.Y() - g.Descent)
instancedData = append(instancedData, []float32{
g.U, g.V,
color.R(), color.G(), color.B(), color.A(), //Color
roundF32(drawPos.X()), roundF32(drawPos.Y()), drawPos.Z(), //Model pos
scale.X(), scale.Y(), //Model scale
}...)
//Add the glyph information to the vbo
startIndex := gr.GlyphCount * floatsPerGlyph
//UV
gr.GlyphVBO[startIndex+0] = g.U
gr.GlyphVBO[startIndex+1] = g.V
//Color
gr.GlyphVBO[startIndex+2] = color.R()
gr.GlyphVBO[startIndex+3] = color.G()
gr.GlyphVBO[startIndex+4] = color.B()
gr.GlyphVBO[startIndex+5] = color.A()
//Model Pos
gr.GlyphVBO[startIndex+6] = roundF32(drawPos.X())
gr.GlyphVBO[startIndex+7] = roundF32(drawPos.Y())
gr.GlyphVBO[startIndex+8] = drawPos.Z()
//Model Scale
gr.GlyphVBO[startIndex+9] = scale.X()
gr.GlyphVBO[startIndex+10] = scale.Y()
gr.GlyphCount++
pos.SetX(pos.X() + advanceF32)
}
gr.GlyphVBO = append(gr.GlyphVBO, instancedData...)
//If we fill the buffer we issue a draw call
if gr.GlyphCount == maxGlyphsPerBatch {
gr.Draw()
}
}
}
func (gr *GlyphRend) Draw() {
@ -92,14 +117,12 @@ func (gr *GlyphRend) Draw() {
return
}
gr.InstancedBuf.SetData(gr.GlyphVBO)
gr.InstancedBuf.SetData(gr.GlyphVBO[:gr.GlyphCount*floatsPerGlyph])
gr.InstancedBuf.Bind()
gr.GlyphMat.Bind()
gl.DrawElementsInstanced(gl.TRIANGLES, gr.GlyphMesh.Buf.IndexBufCount, gl.UNSIGNED_INT, gl.PtrOffset(0), gr.GlyphCount)
gr.GlyphCount = 0
gr.GlyphVBO = []float32{}
}
//SetFace updates the underlying font atlas used by the glyph renderer.
@ -178,7 +201,7 @@ func NewGlyphRend(fontFile string, fontOptions *truetype.Options, screenWidth, s
gr := &GlyphRend{
GlyphCount: 0,
GlyphVBO: make([]float32, 0),
GlyphVBO: make([]float32, floatsPerGlyph*maxGlyphsPerBatch),
}
//Create glyph mesh